Exhaust aftertreatment systems typically include one or more exhaust treatment catalyst elements, including diesel oxidation catalysts (DOC), diesel particulate filters (DPF), and SCR catalysts. Certain exhaust aftertreatment systems may rely on the NH3 sensor as a control element. A failure in the NH3 sensor may significantly impact the control of the exhaust aftertreatment system relying upon the NH3 sensor. Because the exhaust aftertreatment system relies upon the NH3 sensor outputs in certain applications, diagnosis of a faulty or failing sensor can be used to isolate the cause of a faulty or performance condition of the aftertreatment system and take appropriate corrective actions.